1. Field of the Invention
The present invention is directed to certain esters of m-hydroxy-.alpha.-[(methylamino)methyl]benzyl alcohols and their pharmaceutically acceptable acid addition salts.
Upon administration, these compounds will enzymatically "cleave" and release optically active m-hydroxy-.alpha.-[(methylamino)-methyl]benzyl alcohol (phenylephrine), the therapeutically active moiety thereof.
2. Description of the Prior Art
U.S. Pat. No. 3,825,583 -- Hussain and Truelove, discloses and claims an ester of m-hydroxy-.alpha.-[(methylamino)methyl]benzyl alcohol, namely, m(3-)-pivaloxy-.alpha.-[(methylamino)methyl]benzyl alcohol.
A review of the manner in which this compound is prepared readily reveals that a racemic mixture (a mixture containing both the biologically active and the biologically non-active isomer) is obtained. Since the "R" isomer is the only isomer exhibiting substantial therapeutic activity, to date, (R)-m-pivaloxy-.alpha.-[(methylamino)methyl]benzyl alcohol is normally administered in the form of a racemic mixture as the means to separate the optically active form from the racemic mixture has not been devised to date.
Therefore, a need exists for a means to synthesize the optically active form of certain m-acyloxy-.alpha.-[(methylamino)methyl]benzyl alcohols of which m-pivaloxy-.alpha.-[(methylamino)methyl]benzyl alcohol is so among and thus avoid the need to obtain and use a racemic mixture thereof.
In addition to the foregoing, it is obviously apparent that since only the active isomer of the compounds described herein is therapeutically active, the dosage amount of a racemic mixture containing the same required to achieve therapeusis is much greater than that which would be required if the optically active form were administered, per se. Thus, an ancillary need exists for a means to synthesize the optically active isomer, per se, for the sake of minimizing the therapeutic dose required as well as to avoid any toxic reactions which may occur.